Accessible computer systems have proven susceptible to various attacks by computer hackers. In one type of computer attack, a hacker attempts to gain unauthorized access to an online computer service. In this type of attack, the hacker may attempt to crack the password associated with the known logon identification. The hacker may use a computer program that associates passwords with the logon identification in rapid succession. This type of attack may allow the hacker to gain unauthorized access to a particular user's personal account on the online computer service. The hacker also may attempt to use the unauthorized access to sabotage the online computer service. When subject to such attacks, accessible computer systems may be forced to cease operation.